When George Zimmerman shot and killed Trayvon Martin on Feb. 26 in Sanford, Fla., did he act in self-defense or out of some combination of fear, confusion, and racism? The facts remain in dispute. What is not in dispute is that an unarmed 17-year-old African-American wearing a hooded sweatshirt died unnecessarily and far too young.

On Friday, as a commentary on the Martin case, LeBron James posted on his Twitter account a photograph of himself and 12 Miami Heat teammates posing with bowed heads and wearing hooded sweatshirts. One of the hashtags James used was “WeWantJustice.’’

It’s a remarkable image - simple, reserved, eloquent. The eloquence is there regardless of whether anyone seeing it has any knowledge of the Martin case or of the photograph’s connection to it. The players’ body language tells us that something grave is being commemorated. It’s a gravity beyond words. A placard or protest sign would trivialize the image. So much of what makes the photograph so powerful has to do with how it transcends what is in dispute to get at that which is indisputable. The Heat players aren’t addressing the law and controversy, but morality and grief.

The image alludes to the hood having become a symbol of Martin’s death. Zimmerman described Martin’s hoodie when he called police, saying Martin looked “suspicious.’’ People have since been taking photos of themselves in hooded sweatshirts and posting them on the Web. A “Million Hoodie March’’ took place in New York last Wednesday. On Friday, Fox News personality Geraldo Rivera offered his interpretation of the hood’s role in the case. He said on “Fox and Friends,’’ “I think the hoodie is as much responsible for Trayvon Martin’s death . . . as George Zimmerman was.’’

Such an implied connection between criminality and hooded sweatshirts might surprise Mark Zuckerberg or Bill Belichick. That said, an association between hood and illegality goes as far back as medieval times. Robin Hood robbed from the rich to give to the poor, but it was still robbery. Hoods conceal or obscure. They can disguise or seem menacing. Such terms as “hoodlum’’ and “hood’’ bespeak this tradition. In a different way, the ’hood can be a dangerous urban area, as in the 1991 film “Boyz n the Hood.’’

Another tradition also dates to medieval times, the hood and spirituality. This is the tradition the photograph evokes. Ignore the Heat logo on 12 of the sweatshirts. (One of the photo’s several striking aspects is how it uses athletic garb, something designed for motion, to create a sense of stillness.) This group of hooded young men could be monks or religious figures of some other kind - each a version of the several renderings of St. Francis of Assisi by the 17th-century Spanish painter Francisco de Zurbarán, or Augustus Saint-Gaudens’s sculpture, commonly known as “Grief,’’ at the Adams Memorial, in Washington, D.C.

A religious aspect even extends to the background. The photograph was taken in the hotel where the team was staying, in Birmingham, Mich. Behind the players is the sort of garish wallpaper found in a corridor or banquet room. An overly busy floral pattern and harsh lighting combine to make the photograph vaguely resemble a Byzantine or Orthodox icon.

Zurbarán? Saint-Gaudens? Religious icons? Presumably, none of the Heat majored in art history. They didn’t need to. The visual motifs those artists drew on were already old then -and as fresh as they are now. They run that deep in our culture, and that’s what James and his teammates understood. They’re what anyone looking at the photograph responds to.

The players avert their eyes, indicating humility. Their heads are downcast, a designation of mourning, as is the darkness of their attire. The players keep their hands in their pockets, in dejection or resignation. The knowledge that these young men are millionaire celebrities makes their looking like this all the more startling.

It’s true that hands kept in pockets can also suggest packing a pistol, or pretending to. It’s one of the classic hoodlum poses. But there’s no sense of threat in this image. This isn’t a gang. It’s a team. That the players wear their Heat sweatshirts reminds us of that. Notice, too, that we can’t see their numbers - just as we can’t really make out their faces. Anonymity underscores unanimity. A team, after all, is about shared purpose, whether the outcome is victory or defeat. There’s safety in numbers, the saying goes. Yet there’s no sadness like the sadness of numbers. Call it shared sorrow.

What may be the most famous image of athletes making a political statement took place at the 1968 Summer Olympics, when Tommie Smith and John Carlos gave the Black Power salute on the medal stand in Mexico City. They, too, have averted eyes and downcast heads, but it’s their gloved hands and upthrust arms that draw the eye. Few images capture so well the tumult of that particular year. What makes the Heat photograph terrible as well as moving is that it’s timeless - or as timeless, at least, as injustice and death.